The present proposal is based on the view that insulin exerts its multiple metabolic effects by acting at the plasma membrane, and further that a single mechanism may be found to underlie all of the hormone's actions. Three general approaches willbe used. First, attempts will be made to demonstrate an effect of the hormone on isolated plasma membranes. Current evidence indicates that purified membranes of insulin-responsive tissues such as adipose cells readily bind insulin but show no "effect" from the hormone. We wish to look for the factor(s) necessary to translate insulin "binding" into accelerated glucose transport; this will be done by re-addition of individual cell components and by various perturbations of the isolate membranes themselves. Secondaly, plasma membranes can now be prepared with a "built-in" insulin effect if the whole cell is exposed to the hormone prior to rupture. We will attempt to find differences between the "insulin" and control membranes in terms of over-all structure or protein configuration in the membranes. Finally, attempts will be made to develop antisera against whole and ensymatically modified membranes with the objective of isolating specific antibodies directed against both the glucose transport mechanism (? carrier protein) and the insulin-binding site. This may permit isolation of either or both of these structures by affinity chromatography and further allow examination of the interdependence of the two membrane "sites."